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chapter 2 the computer
The Computer a computer system is made up of various elements each of these elements affects the interaction – input devices – text entry and pointing – output devices – screen (small&large), digital paper – virtual reality – special interaction and display devices – physical interaction – e. g. sound, haptic, bio-sensing – paper – as output (print) and input (scan) – memory – RAM & permanent media, capacity & access – processing – speed of processing, networks
Interacting with computers to understand human–computer interaction … need to understand computers! what goes in and out devices, paper, sensors, etc. what can it do? memory, processing, networks
A ‘typical’ computer system ? • screen, or monitor, on which there are windows • keyboard • mouse/trackpad • variations – desktop – laptop – PDA the devices dictate the styles of interaction that the system supports If we use different devices, then the interface will support a different style of interaction
How many … • computers in your house? – hands up, … … none, 1, 2 , 3, more!! • computers in your pockets? are you thinking … … PC, laptop, PDA ? ?
How many computers … in your house? – PC – TV, VCR, DVD, Hi. Fi, cable/satellite TV – microwave, cooker, washing machine – central heating – security system can you think of more? in your pockets? – PDA – phone, camera – smart card, card with magnetic strip? – electronic car key – USB memory try your pockets and bags
Interactivity? Long ago in a galaxy far away … batch processing – punched card stacks or large data files prepared – long wait …. – line printer output … and if it is not right … Now most computing is interactive – rapid feedback – the user in control (most of the time) – doing rather than thinking … Is faster always better?
Richer interaction sensors and devices everywhere
text entry devices keyboards (QWERTY et al. ) chord keyboards, phone pads handwriting, speech
Keyboards • Most common text input device • Allows rapid entry of text by experienced users • Keypress closes connection, causing a character code to be sent • Usually connected by cable, but can be wireless
layout – QWERTY • Standardised layout but … – non-alphanumeric keys are placed differently – accented symbols needed for different scripts – minor differences between UK and USA keyboards • QWERTY arrangement not optimal for typing – layout to prevent typewriters jamming! • Alternative designs allow faster typing but large social base of QWERTY typists produces reluctance to change.
alternative keyboard layouts Alphabetic – keys arranged in alphabetic order – not faster for trained typists – not faster for beginners either! Dvorak – – – common letters under dominant fingers biased towards right hand common combinations of letters alternate between hands 10 -15% improvement in speed and reduction in fatigue But - large social base of QWERTY typists produce market pressures not to change
phone pad and T 9 entry • use numeric keys with multiple presses 2 3 4 5 –abc -def -ghi -jkl 6 7 8 9 - mno pqrs tuv wxyz hello = 4433555[pause]555666 surprisingly fast! • T 9 predictive entry – – type as if single key for each letter use dictionary to ‘guess’ the right word hello = 43556 … but 26 -> menu ‘am’ or ‘an’
Handwriting recognition • Text can be input into the computer, using a pen and a digesting tablet – natural interaction • Technical problems: – capturing all useful information - stroke path, pressure, etc. in a natural manner – segmenting joined up writing into individual letters – interpreting individual letters – coping with different styles of handwriting • Used in PDAs, and tablet computers … … leave the keyboard on the desk!
Speech recognition • Improving rapidly • Most successful when: – single user – initial training and learns peculiarities – limited vocabulary systems • Problems with – – external noise interfering imprecision of pronunciation large vocabularies different speakers
Numeric keypads • for entering numbers quickly: – calculator, PC keyboard • for telephones 1 not the same!! ATM like phone 2 3 7 8 9 4 5 6 7 8 9 1 2 3 * 0 # 0 . = telephone calculator
positioning, pointing and drawing mouse, touchpad trackballs, joysticks etc. touch screens, tablets eyegaze
the Mouse • Handheld pointing device – very common – easy to use • Two characteristics – planar movement – buttons (usually from 1 to 3 buttons on top, used for making a selection, indicating an option, or to initiate drawing etc. )
the mouse (ctd) Mouse located on desktop – requires physical space – no arm fatigue Relative movement only is detectable. Movement of mouse moves screen cursor Screen cursor oriented in (x, y) plane, mouse movement in (x, z) plane … … an indirect manipulation device. – device itself doesn’t obscure screen, is accurate and fast. – hand-eye coordination problems for novice users
How does it work? Two methods for detecting motion • Mechanical – Ball on underside of mouse turns as mouse is moved – Rotates orthogonal potentiometers – Can be used on almost any flat surface • Optical – – light emitting diode on underside of mouse may use special grid-like pad or just on desk less susceptible to dust and dirt detects fluctuating alterations in reflected light intensity to calculate relative motion in (x, z) plane
Even by foot … • some experiments with the footmouse – controlling mouse movement with feet … – not very common : -) • but foot controls are common elsewhere: – car pedals – sewing machine speed control – organ and piano pedals
Touchpad • small touch sensitive tablets • ‘stroke’ to move mouse pointer • used mainly in laptop computers • good ‘acceleration’ settings important – fast stroke • lots of pixels per inch moved • initial movement to the target – slow stroke • less pixels per inch • for accurate positioning
Trackball and thumbwheels Trackball – ball is rotated inside static housing • like an upsdie down mouse! – – – relative motion moves cursor indirect device, fairly accurate separate buttons for picking very fast for gaming used in some portable and notebook computers. Thumbwheels … – for accurate CAD – two dials for X-Y cursor position – for fast scrolling – single dial on mouse
Joystick – indirect pressure of stick = velocity of movement – buttons for selection on top or on front like a trigger – often used for computer games aircraft controls and 3 D navigation
Touch-sensitive screen • Detect the presence of finger or stylus on the screen. – works by interrupting matrix of light beams, capacitance changes or ultrasonic reflections – direct pointing device • Advantages: – fast, and requires no specialised pointer – good for menu selection – suitable for use in hostile environment: clean and safe from damage. • Disadvantages: – finger can mark screen – imprecise (finger is a fairly blunt instrument!) • difficult to select small regions or perform accurate drawing – lifting arm can be tiring
Stylus and light pen Stylus – small pen-like pointer to draw directly on screen – may use touch sensitive surface or magnetic detection – used in PDA, tablets PCs and drawing tables Light Pen – now rarely used – uses light from screen to detect location BOTH … – very direct and obvious to use – but can obscure screen
Digitizing tablet • Mouse like-device with cross hairs • used on special surface - rather like stylus • very accurate - used for digitizing maps
Eyegaze • control interface by eye gaze direction – e. g. look at a menu item to select it • uses laser beam reflected off retina – … a very low power laser! • • mainly used for evaluation (ch x) potential for hands-free control high accuracy requires headset cheaper and lower accuracy devices available sit under the screen like a small webcam
Multitouch, gestural • Good points? • Bad points?